Steam generator with forced circulation



Sept. 16, 1941. H.

PETERS 2,256,169

STEAM GENERATOR WITH FORGED CIRCULATION Filed March 51, 1938 2 Sheets-Sheet flame/c PETFRS QWWW ATTORNEYS Sept. 16, 1941. PETERS 2,256,169

STEAM GENERATOR WITH FORCED CIRCULATION Filed March 31, 1938 2 Shets-Sheet 2 IN v EN ro R HEINRICH PETEES ATTORNEYS Patented Sept. 16, 194-1 Heinrich Peters, Berlin, Germany, assignor to: La

Mont Corporation, New York, N..Y., a corporation of New York Application March 31, 1938, Serial N0. 199,144 In Germany November 28, 1936 11 Claims; I

This invention relates to forced circulation steam generators of the so-called drumless type and a general object of the invention is to improve the operation of such steam generators when subjected to marked variations in loading.

Drumless forced circulation steam generators, that is, drumless steam generators in which a portion of the Water forcedv through the generating elements is recirculated, usually comprise mechanical means, such, for example, as. centrifugal steam separators, for effecting the separation of the steam and Water, the Water thus separated being returned by the circulating mechanism to the steam generating tubes and the steam being usually conducted to a superheater before being used. In steam generators of this type with great variations of loading, especially in railroading or in ship driving, it can happen that the water forced suddenly out of. the heating surfaces by the increaseof loading cannot be handled by the centrifugal separator; and a part will pass over into the conduit to the superheater. Proposals are already known so to insert a balancing reservoir between the pressure conduit of that part of the heatingsurface working with the forced circulation and the steamreceiving conduit that the height of the wamr. layer in the balancing reservoir keeps inbalance the pressure difierence arising between the two.conduits. Since the pressure difierence with forced circulation boilers usually amounts to two to three atmospheres, there isrequired atheight of the balancingreservoir of 30m 40 meters above the separator. The already suggested arrangement of a balancing reservoir cannot, therefore, be carried out practically inmost cases. Besides, the balancing reservoir so inserted has the disadvantage that with every variation in the propelling pressure which arises independently of the steam formation as, for example, through variation in the number of revolutions or the like, considerable variations in the water level in the balancing reservoir take place.

Through the following proposals in this invention are such difficulties completely avoided'and indeed it is proposed toprovide balancing or torcan be utilizedi Alsothe control could beindependent of the propellingpressure'of the circulating apparatus, that is, also of the Water velocity in the pressure circuit".

Figure 1 is a diagrammatic elevation of one embodiment of the invention in which the stabilizing reservoir hasone of its connections to the generator circuit on the'pressure side of the circulating mechanism and the other connection on the suction side;

Figure 2 is a diagrammatic" elevation of another embodiment of the invention in which the stabilizing reservoir has both its connections to the conduit for the steam and water mixture;

Figure 3 is a diagrammatic elevation in which the stabilizing reservoir has one of its connections to the steam and water conduit and its other connection to the steam conduit.

The possibility of balancing or stabilizing reservoirs is more fully represented in Figs. 1. to 3. In Figure. 1 the steam generator consists of three parts. In the part 421a preheating of. the water takes place principally, while in the part 43 the steam generation takes place. In the heating surface section 44 the steam produced is superheated; A feed pump 45 propels the feed Water through the feed conduit 46 into the preheating section 42. The preheated water passes through a conduit 41and 48 into the distributing header 49 of the steam generator tube bundle. The resultant steam and water mixture is collected in the collecting header 5B and flows through a conduit 5| to a rotating centrifugal separator 52. In this separator the steam is separated from the steam water mixture. Thesteam is conducted from the center of the centrifugal separator through the conduit 53 to the superheater. The water centrifuged in the separator flows back through the outlet 54 and the conduit 48 to the distributing header 49 of the heating surface bundle 43.

The water film forming in the separator is dependent on the Water content of the steam water mixture. The greater. the Water film the higher the propelling pressure. According to the invention the feeding is regulated through this propelling pressure so that, therefore, by a raising of the propelling pressure through a controlling valve 55 the amount of water fed in is throttled.

There is now connected to the circuit a balancing or-stabilizing reservoir 56. This balancing or stabilizing-reservoir is so arranged according to Figure 1 that by the overstepping of a predetermined pressure of the circulating apparatus a conduit 58 to the balancing or stabilizing reser is so measured that the flowing out of the water content can take place only comparatively slowly.

The building in of a regulating valve 66 is useful. At the upper end of the balancing or stabilizing reservoir is a conduit, 66 likewise connected with the mixture conduit 5|. The two connections to the mixture conduit 5| are preferably located close beside each other whereby no noteworthy pressure differences can arise between the two points of connection and so that only narrow pressure diiferences can, therefore,

form between'the connecting points even with great steam generation in the heatinglsurface section 43 and great flow velocity in the mixture conduit 5|. The balancing or stabilizingreservoir 56 is, therefore, normally completely emptied of water and serves the purpose of compensating for any sudden rush of water out of the heating surfaces.

By the shutting down of the boiler the equalizing or stabilizing reservoir cannot fill itself with water. There is thereby obtained by the arrangement the result that, through a high propelling pressure of the circulating apparatus, a part of the capacity of the heating surface is immediately released for steam. Alsoit is not to be feared that water will be entrained into the conduit 53 to the superheater. There can also be located in the pressure conduit of the circulating circuit a check valve 6| which is to prevent the heating surface, after shutting down of the circulating mechanism, from emptying itself; The mixture conduit 5| is likewise so arranged that an emptying of the heating surface is not possible. When, in operation, a drawing off of the water from the balancing or stabilizing reservoir is. necessary, this can take place with the help of the conduit 65.

According to Figure 2 it is further proposed to connect the balancing orstabilizing reservoir 56 merely to the mixture conduit 5|. The lower part of the balancing or stabilizing reservoir 56 is connected by a conduit 62 with the mixture con.- duit 5| and this conduit 62 is so arranged that there is a sump in it. At the junction of the conduit 52 with the mixture conduit 5| the mixture conduit 5| has a sharp bend so that the water present in the mixture is, through centrifugal force, centrifuged into the entrance of the connecting conduit 62 and it is then to be reckoned therewith that the water sump is always filled full of water. The second connection to the mixture conduit 5| through the conduit 63 is so arranged on the mixture conduit 5| that between the two points of connection arises a so much greater pressure fall that by maximum flow in the mixture conduit 5| resulting from a sudden increase in the steam demand the balancing or stabilizing reservoir 56 is filled as full as possible with water. I

In case this arrangement is not-permitted it is advantageous to provide -a throttling place 64 between the two connecting .points in the mixture conduit 5|. This throttling place can advantageously be provided in the form of a valve so to the superheater.

that it is possible to regulate the pressure fall in accordance with the demands. The arrangement in the mixture conduit is very advantageous since both the resistances in the mixture conduit and also the rush of water out of the heating surfaces vary approximately lineally with the steam performance. When the balancing or stabilizing reservoir is constructed in cylindrical form the result is obtained that, corresponding to the varying heating of the heating surface section 43, the mass of water forced into or additionally taken up in the balancing or stabilizing reservoir is substantially uniform. The control operates completely automatically without special control apparatus being necessary,

According to Figure 3 it is proposed to provide a balancing or stabilizing reservoir between the mixture conduit and the separated steam conduit This control works quite similarly to that described in Figure 2. The connection 62 to the mixture conduit 5| is again provided with a water sump. The upper connection'of the reservoir is carried to the separated steam conduit, or'the separated steam conduit is carried through the upper space of the balancing or stabilizing reservoir, whereby a still further drying of the steam is obtained. The choice of the connecting point to the saturated steam conduit is again so selected that with large steaming performance the pressure differences between the connecting points are so great that the balancing or stabilizing reservoir is filled with water. With this connection the situation arises that the pressure differences between the two connecting points increase approximately as the square of the steam release while the water pressure out of the heating surfaces is dependent only lineally on the steam production. It is therefore advantageous so to construct the balancing or stabilizing reservoir 55 that with the provision of a vertical reservoir the cross section,

tapers off upwardly. The same result can be obtained in the following manner, namely, that, as illustrated by way of example in Figure 3, a tube bent from the horizontal into the vertical can be utilized asa balancing or stabilizing reservoir.

The inventive idea is applicable not only to steam generators which work with water, but to the vaporization of any fluid.

The described means for creating a balancing or stabilizing reservoir are also useful with steam generators which work with a once-through flow of the water. With such steam generators, anal-' ogously to the relationship with the forced circulation boilers, the height of location of the bal-' ancing or stabilizing reservoir'determines only the pressure of the propelling mechanism that is necessary for overcoming the fiow'resistance. If, for example, the feed pump of a once through boiler has a pressure of I20 atmospheres and steam of a pressure of atmospheres is produced, then are only the20 atmospheres decisive;

What is claimed as new is:

1. In a forced circulation steam generator, the combination with a generator circuit comprising steam generator tubes, a circulating mechanism connected to the input and to the discharge ends of said tubes and a centrifugal steam separator, a stabilizing reservoir connected to saidcircuit, said stabilizing reservoir being so located and so connected with said circuit that water in excess of that which can properly be handled in said circuit at a given time may be directed into said reservoir for later discharge again into said circuit, and means for insuring such direction of the excess water under predetermined pressure conditions in said circuit between the discharge ends of said generator tubes and the intake of said separator.

2. A steam generator according to claim 1 in which the stabilizing reservoir has one of its connections to said generator circuit on the pressure side of said circulating mechanism and the other connection on the suction side and in which there is a shut off valve controlled by variations in the pressure differences between said two sides of the circuit and located in the connection of said reservoir to the pressure side of said circuit.

3. A steam generator according to claim 1 in which the stabilizing reservoir has one of its connections to said generator circuit on the pressure side of said circulating mechanism and the other connection on the suction side and in which there is a shut-01f valve located in the connection of said reservoir to the pressure side of said circuit, said generator being provided with means governed by the pressure differences between the two sides of said circuit for opening said shut-off valve only when there is a predetermined rise in the pressure difference.

4. A steam generator according to claim 1 in which there is a connection from the stabilizing reservoir to the suction side of the circulating mechanism which is of such small cross section that the water forced into the stabilizing reservoir can only gradually go back through this connection into the circulation.

5. A steam generator according to claim 1 in which there is a steam take-off from said steam separator and in which the stabilizing reservoir has one connection to the circuit on the intake side of said circulating mechanism and another connection to said circuit through said steam take-off.

6. A steam generator according to claim 1 in which there is a steam take-off from the separator and in which the stabilizing reservoir has one connection to the generator on the suction side of the circulating mechanism and another connection to the steam take-01f and in which the connection to the generator circuit on the suction side is provided with a sump.

7. A steam generator according to claim 1 in which there are means governed by the pressure differences in the two parts of said circuit to which the stabilizing reservoir is connected which control the flow of excess water into said stabilizing reservoir and in which adjustable throt tling means are provided for varying the amount of circulation flow required to produce the critical flow determining difference.

8. In a steam generator, steam generating tubes and means connected to the input ends of said tubes for positively forcing water therethrough, a steam separator. connected with the discharge ends of said tubes and a stabilizing reservoir connected in parallel with said generator tubes between the input and discharge ends thereof and so located and so connected with said circuit that water in excess of that which can properly be handled in said circuit at a given time may be directed into said reservoir for later discharge again into said circuit, and means for insuring such direction of the excess water under predetermined pressure conditions in said circuit.

9. In a forced circulation steam generator, the combination with a generator circuit comprising steam generator tubes, a circulating mechanism connected to the input and to the discharge ends of said tubes and a centrifugal steam separator, of a stabilizing reservoir so connected to said circuit on the intake side of said steam separator and in parallel with said intake as to receive tem porarily water in excess of that which can properly be handled in said circuit at a given time, and means for insuring direction of the excess water into said reservoir under predetermined pressure conditions produced by said excess water in said intake.

10. In a forced circulation steam generator comprising steam generating tubes, a circulating mechanism connected to the input and to the discharge ends of said tubes and a centrifugal steam separator, a stabilizing reservoir connected to said circuit, said stabilizing reservoir being so located and so connected with said circuit between the discharge ends of said generator tubes and the intake of said separator that water in excess of that which can properly be handled in said circuit at a given time may be directed into said reservoir for a later discharge again into said circuit, and means responsive to variations in a force varying with the amount of water flowing in the circuit for causing water to flow to and from said stabilizing reservoir in order to control the amount of water to be handled by the centrifugal separator.

11. In a forced circulation steam generator comprising steam generating tubes, a circulating mechanism connected to the input and to the discharge ends of said tubes and a centrifugal steam separator, a stabilizing reservoir connected to said circuit, said stabilizing reservoir being so located and so connected with said circuit that water in excess of that which can properly be handled in said circuit at a given time may be directed into said reservoir for a later discharge again into said circuit, and means responsive to variations in a force varying with variations in the proportion of steam and water in the circuit for causing water to flow to and from said stabilizing reservoir to control the amount of water to be handled by the centrifugal separator.

HEINRICH PETERS. 

